In the process of catalytically converting hydrocarbon oils into valuable lighter products, and in particular in the upgrading of residual hydrocarbon oils, the feedstocks to be used are normally subjected to one or more pre-treatments to substantially reduce the amount of metals and/or sulfur present therein. It is well known that metals and sulfur exert a detrimental effect on the life of catalysts used in conversion processes.
The use of catalysts comprising nickel and/or vanadium on porous carriers such as silica in demetallization processes is well established. Reference is made in this respect to Dutch Patent Specification No. 7309387.
It is known from U.S. Pat. No. 4,102,779 that heavy residual hydrocarbon oils having a high metal content can be demetallized using a Group VIB and/or a Group VIII catalyst. The product obtained has to be subjected to a desulfurization treatment using an appropriate catalyst prior to its use as feedstock in a cracking process.
It is further known from European Patent Specification No. 159097 that catalysts containing exclusively molybdenum in a quantity of more than 2 parts by weight per 100 parts by weight of silica can be used advantageously in the demetallization of heavy hydrocarbon oils having a relatively high C.sub.5 -asphaltenes content and a metal content (Ni+V) of less than 350 parts per million by weight (ppmw), in particular in the demetallization of feedstocks which have been obtained at least partly as a distillation residue of a distillation under reduced pressure of an atmospheric residue. At least part of the oils thus demetallized can be subjected to a further catalytic conversion process.
Hydrodemetallization catalysts as described hereinabove have been made and are generally utilized for the demetallization of vanadium-rich feedstock containing rather small amounts of nickel.
Nickel-rich feedstocks, however, are not demetallized satisfactorily with conventional demetallization catalysts due to their high nickel content so that the product obtained does not qualify as a suitable feed for further catalytic processing.
Therefore, it would be of importance to develop a process for the catalytic conversion of nickel-rich residual hydrocarbon oils based on catalysts which exert sufficient demetallization activity together with sufficient stability (long life-time).
It has now been found that nickel-rich hydrocarbon oils can be satisfactorily demetallized when use is made of certain catalysts operated at rather high hydrogen partial pressures.